In our Advanced RP/RM (rapid prototyping/rapid manufacturing) course, I was discussing the course requirements. One our of requirements is an independent research project and report to be undertaken in teams of two (the project is worth 40% of your grade). As an instructor, I would ask the class at every meeting if they had any ideas for a project.

One of the teams (composed of Adele Klee and Zack Chan) approached me after class.

“Can we talk about our project?”

“What do you think about printing in Chalk?”

“What?” “Why?”

Brains go into overdrive: “Talking to the teacher when I felt like one of the only ones in the class who didn’t really know what was going on was terrifying. I’m not in the major and I suppose I was worried that that would be held against me. I asked about the chalk. It never actually seemed like that great of an idea, but it was mine and I had to have something. I noticed what seemed like disapproval and panicked. My mind was racing. I had to think of something, anything, that’s white and powdery. It shouldn’t be that hard, only two criteria. Find something white- check. Find something powdery- check.”

In a moment of panic:

“What about salt?” “Do you think it will work?”

“Sure, maybe!”

“How do we get started?”

“You’ll need to get the salt in the correct powder size.”

“Get a coffee grinder and start grinding the salt to something super fine!”

“Then do a simple powder distribution by running the powder through 60, 100 and 120 screens.”

This process took place across several weeks. Once they got the salt to something that looked like white dust. They screened the batch through 150 mesh screen.

On to bench testing — to determine how the new powder liked our binders and if not, then test out various additives. Over the next two weeks different sets of adhesives and ratios were tested against our existing binders. Success!!!

They loaded up the 3D printer with the salt mixture and used an existing binder solution. Let’s just say their first 3D printing tests quite successful. The salt powder mix spread extremely well, and produced the best surface finish on the printing-bed surface that we have ever seen. Several adjustments to layer thickness and saturation settings, and amazing parts appeared.

“It was so sudden, absolutely no planning whatsoever, and he liked it! It was so exciting that I, a random, non-mechanical engineering student, would come up with an idea that was good. We ran with it and got amazing results.”

Did we mention that it costs something on the order of $4 for 25 lbs of Salt!

Final Recipe:

Finely Powdered Salt — 8 parts by weight

Maltodextrin — 1 part by weight

It is so much fun to watch the process happen again.

{We’re not sure if this is really a first as we’ve heard some rumors that UCLA Architecture Department might have tried salt printing 10+ years ago. It doesn’t take away the excitement of seeing some of the amazing quality parts being printed.}

Yes that is one of our thoughts exactly, it should dissolve in water there is no chemical reaction that fixes the form it is fixed from recrystallization, however I have not tested this yet I do not know if the dissolving is as aggressive as the sugar sugar powder

I have to ask, why the non-commercial license? That makes it so that folks can’t use this commercially to do things like making things and selling them. That’s a pretty restrictive license for such an awesome technology!

Bre, that’s a great question. I pointed the students to the CC website. I told them to read the information and choose the most appropriate license form. I will forward your response to the Salt Team and report.

I have to ask, why the non-commercial license? That makes it so that folks can’t use this commercially to do things like making things and selling them. That’s a pretty restrictive license for such an awesome technology!

Bre, that’s a great question. I pointed the students to the CC website. I told them to read the information and choose the most appropriate license form. I will forward your response to the Salt Team and report.

FAIL – We tried salt prints with Cargill Alberger® Shur-Flo® Fine Flour Salt (screening 70-200). After many attempts (including screening the salt to a finer size) We simply couldn’t get the machine to lay out additive layers without dragging the previous layers across the build bed. The Shur-Flo salt is courser than expected, so when we get a chance we’re going to try to source a finer salt to see if it “packs in” the build bed more firmly…

All really successful powder needs to be in the 20-100 micron size range (check the original papers by Sachs & Cima) that means it needs to be screened at 200 mesh but 300 mesh would be better. We used a coffee grinder to make the particles smaller.

FAIL – We tried salt prints with Cargill Alberger® Shur-Flo® Fine Flour Salt (screening 70-200). After many attempts (including screening the salt to a finer size) We simply couldn’t get the machine to lay out additive layers without dragging the previous layers across the build bed. The Shur-Flo salt is courser than expected, so when we get a chance we’re going to try to source a finer salt to see if it “packs in” the build bed more firmly…

All really successful powder needs to be in the 20-100 micron size range (check the original papers by Sachs & Cima) that means it needs to be screened at 200 mesh but 300 mesh would be better. We used a coffee grinder to make the particles smaller.

hmmm. I wonder if when grinding, you actually produce a range of particle size. the reason i mention this is because this is exactly what you intentionally make in the sugar-sugar recipe. and having the right ratio of particle size seems important in that recipe. too much course material and it ‘drags’ as UNMD describes, too much fine material spreading’s difficult and resolution is poor.

hmmm. I wonder if when grinding, you actually produce a range of particle size. the reason i mention this is because this is exactly what you intentionally make in the sugar-sugar recipe. and having the right ratio of particle size seems important in that recipe. too much course material and it ‘drags’ as UNMD describes, too much fine material spreading’s difficult and resolution is poor.

It would be wonderful to read their report! Have they tried mixing fillers into the salt to improve the strength of the final product? Off the top of my head, it seems like 5–10% of montmorillonite might improve the strength substantially, if you can get the salt to bind to it. (Other aggregates like fine silica sand or asbestos might work as well or better, but those bring up some serious safety problems.)

It would be wonderful to read their report! Have they tried mixing fillers into the salt to improve the strength of the final product? Off the top of my head, it seems like 5–10% of montmorillonite might improve the strength substantially, if you can get the salt to bind to it. (Other aggregates like fine silica sand or asbestos might work as well or better, but those bring up some serious safety problems.)

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I am Dixit from India. I will be buying Z 450 shortly. I was looking for alternate materials for Visijet PXL Core. I find this site very interesting. It is giving me all kinds of solutions I was looking for.